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All sourcesNASA NTRSDOE OSTI
NASA NTRS2024

Ternary Feldspar Within Felste Clasts From Apollo Impact Melt Breccia 72255

Granitic clasts with unique ternary feldspar compositions have been identified within samples of the layered impact melt breccia from Apollo 17 Station 2 Boulder 1 (72215, 72235, 72255 and 72275), and in a felsite clast from station 3 (73215). These “ternary” compositions seemingly plot within the miscibility gap of the albite-anorthite-orthoclase (Ab-An-Or) system. Feldspars with these compositions have not been identified in terrestrial samples, and equilibrium feldspar compositions from laboratory experiments indicate they would not be thermodynamically stable. Thus, the physiochemical processes involved in forming these unique ternary feldspars remain poorly understood. To better constrain the formation of ternary feldspar within lunar breccias, we have undertaken a coordinated scanning electron microscope (SEM)-based coupled electron backscatter diffraction (EBSD) and energy dispersive spectrometry (EDS), electron microprobe analyzer (EPMA) wavelength dispersive spectrometry, and transmission electron microscopy (TEM) study. The goals of this study are twofold: 1) confirm whether ternary feldspar is present as coherent, single-crystals or sub-microscopic intergrowths of normal compositions, and 2) better constrain the formation conditions of clasts containing ternary feldspar.

T. M. Erickson↗
NASA NTRS1993

Age and thermochronology of K-feldspars from the Manson Impact Structure

As a contribution to the effort to obtain a precise age for the Manson Impact Structure, we are approaching the problem from a thermo chronological perspective, with the goal of extracting an age from Ar-40/Ar-39 age-spectrum analysis of partially overprinted K-feldspars taken from granitoid clasts. We find that shocked feldspars from Manson generally show a strong overprint in their age spectra, with more than 50 percent of each spectrum being reset. The reset portions of the age spectra correspond to gas lost from very small diffusion domains, and a characteristic of the Manson samples is the very large range in apparent diffusion dimensions that they display, with the smallest domains being some 400 times smaller than the largest domains. It is also noteworthy that the small domains comprise a substantial portion of the volume of the feldspars (50 percent or more). These observations are consistent with the extreme shock experienced by these samples. In detail, the spectra we have measured to date are saddle-shaped and show minimum ages of between 67 and 72 Ma, which we interpret to be maximum estimates for the age of the impact. In the case of one sample (M1-678.3; K-feldspar from a large syenite block located well below the apparent melt-matrix breccia in the M1 borehole), isotope correlation analysis suggests the presence of a non-atmospheric trapped Ar component (Ar-40/Ar-36 of 660 plus or minus 40), and an age of about 65.3 plus or minus 0.5 Ma (2 sigma). Our interpretation of our results is that the shock of impact greatly reduced the diffusion-domain sizes of our samples, making them susceptible to significant Ar loss during heating associated with impact. It appears that while our feldspars were partially open to Ar loss, they equilibrated with a non-atmospheric Ar component, probably related to impact-related degassing of old basement around the impact site.

Zeitler, P. K.↗
NASA NTRS2020

Asteroid Cooling Rates Indicated by K-Feldspar Exsolution Textures in H4 Ordinary Chondrites

Undisturbed thermal metamorphism in ordinary chondrite (OC) asteroids, produced through the radioactive decay of 26Al, is expected to result in an onion-shell-like structure. In such a structure, the inner layers of the asteroid experience more extensive thermal metamorphism, as represented by higher petrologic type, than the exterior layers. Furthermore, cooling rates are expected to be slower for OCs of high petrologic type than those of low petrologic type. However, cooling rates determined using metallographic methods and pyroxene diffusion are inconsistent with onion-shell-style cooling and have resulted in new models. These models argue for the disruption of the asteroid after peak metamorphism followed by reaccretion into a rubble pile. Improved constraints on cooling rates would provide a better understanding of the timing and scale of disruptive events. Feldspar microtextures are another tool that can be used to determine asteroid cooling rates. In OC chondrules, plagioclase is present as either a primary phase, or a secondary phase forming from the crystallization of mesostasis glass through petrologic type 4, followed by chemical and textural equilibration. Potas-sium feldspar is observed in petrologic types 3.6-6, as either patches or lamellae exsolved from albite in a perthite texture, often near pores or fractures. Exsolution occurs most commonly, and most extensively, in petrologic type 4. Because the feldspar exsolution wavelength is related to the rate at which grains cooled from the solvus temperature, determined from the mineral’s bulk composition, the chondrite cooling rate can be measured from regions of exsolution. We have previously reported the perthite exsolution cooling rate of Avanhandava, an H4 chondrite, to be 1 °C per 1-4 months over a temperature interval of 765-670 °C. A peristerite exsolution texture was also present in the Na-rich lamellae for which we estimated a cooling rate of 1 °C in 103-104 years from 570-540 °C. Overall, the cooling rates determined from Avanhandava are consistent with pyroxene diffusion (fast cooling at high temperatures) and metallographic rates (slow cooling at low temperatures), hence with the rubble pile model of disruption and reaccretion. Here, we characterize feldspar microtextures in four additional H4 chondrites to test the consistency of feldspar cooling rates across a range of samples. We show that all H4s are similar and support rubble pile models.

Lewis, J. A.↗
NASA NTRS2019

A Recent Volcanic Eruption, Holuhraun, in the Central Highlands of Iceland as a Mars analog: The 2018 Field Campaign of FELDSPAR

In summer 2018, FELDSPAR conducted an analog sampling expedition to the Holuhraun volcanoin the central highlands of Iceland that erupted from August 2014 to February 2015. Holuhraun hassteep gradients within an otherwise relatively controlled region, and thus served as the primaryMars analog site for the 2018 FELDSPAR field campaign. Samples along gradients of mineralogyas measured via near-IR and visible reflectance spectroscopy, temperature as measured by an IRprobe, and physical location about the fissure (slope incline, directionality, height up the slope,etc.) were analyzed in-field with reflectance spectroscopy and X-ray fluorescence, in the field labfor adenosine trisphosphate (ATP) as an indicator of metabolic activity, and after return to thehome lab for both geochemical and geophysical parameters (moisture content, grain size, X-raydiffraction) and biochemical parameters (DNA content and speciation). This abstract representsthe first report on the 2018 field campaign with initial results and interpretation. This work is part ofField Exploration and Life Detection Sampling for Planetary Analogue Research (FELDSPAR), onFacebook @FELDSPAResearch.

Volcanic↗
NASA NTRS1977

Particle size and X-ray analysis of Feldspar, Calvert, Ball, and Jordan soils

Pipette analysis and X-ray diffraction techniques were employed to characterize the particle size distribution and clay mineral content of the feldspar, calvert, ball, and jordan soils. In general, the ball, calvert, and jordan soils were primarily clay size particles composed of kaolinite and illite whereas the feldspar soil was primarily silt-size particles composed of quartz and feldspar minerals.

Chapman, R. S.↗
NASA NTRS1978

Plagioclase feldspars - Visible and near infrared diffuse reflectance spectra as applied to remote sensing

Visible and near IR diffuse reflectance spectra of plagioclase feldspars are characterized by absorption features caused by minor amounts of Fe(2+) that occur bound in the crystal structure. It is found that identification of terrestrial feldspars by remote sensing appears to be feasible for the compositional range An50 to An80, providing that other minerals do not mask the feldspar signatures. Determination of plagioclase composition using the wavelength of the Fe(2+) band may be possible for lunar samples, where the plagioclase can be assumed to be more calcic than An65.

Adams, J. B.↗
NASA NTRS2003

Raman Spectroscopic Characterization of the Feldspars: Implications for Surface Mineral Characterization in Planetary Exploration

The availability in the last decade of improved Raman instrumentation using small, stable, intense lasers, sensitive CCD array detectors, and advanced fast grating systems enabled us to develop the Mars Microbeam Raman Spectrometer (MMRS), a field-portable Raman spectrometer with precision and accuracy capable of identifying minerals and their different compositions. For example, we can determine Mg cation ratios in pyroxenes and olivines to +/-0.1 on the basis of Raman peak positions. Feldspar is another major mineral formed in igneous systems whose characterization is important for determining rock petrogenesis and alteration. From their Raman spectral pattern, feldspars can be readily distinguished from ortho- and chain-silicates and from other tecto-silicates such as quartz and zeolites. We show here how well Raman spectral analysis can distinguish among members within the feldspar group.

Freeman, J. J.↗
NASA NTRS2022

Identifying Shocked Feldspar on Mars Using Perseverance Spectroscopic Instruments: Implications for Geochronology Studies on Returned Samples

The Perseverance rover (Mars 2020) mission, the first step in NASA’s Mars Sample Return (MSR) program, will select samples for caching based on their potential to improve understanding Mars’ astrobiological, geological, geochemical, and climatic evolution. Geochronologic analyses will be among the key measurements planned for returned samples. Assessing a sample’s shock history will be critical because shock metamorphism could influence apparent sample age. Shock effects in one Mars-relevant mineral class, plagioclase feldspar, have been well- documented using various spectroscopy techniques (thermal infrared reflectance, emission, and transmission spectroscopy, Raman, and luminescence). A subset of these data will be obtained with the SuperCam and SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instruments onboard Perseverance to inform caching decisions for MSR. Here, we review shock indicators in plagioclase feldspar as revealed in Raman, luminescence, and IR spectroscopy lab data, with an emphasis on Raman spectroscopy. We consider how this information may inform caching decisions for selecting optimal samples for geochronology measurements. We then identify challenges and make recommendations for both in situ measurements performed with SuperCam and SHERLOC and for supporting lab studies to enhance the success of geochronologic analyses after return to Earth.

mars↗
NASA NTRS1972

Quartz and feldspar glasses produced by natural and experimental shock.

Refractive index, density, and infrared absorption studies of naturally and experimentally shocked-produced glasses formed from quartz, plagioclase, and alkali-feldspar confirm the existence of two main groups of amorphous forms of the framework silicates: solid-state and liquid-state glasses. These were apparently formed as metastable release products of high-pressure-phases above and below the glass transition temperatures. Solid-state glasses exhibit a series of structural states with increasing disorder caused by increasing shock pressures and temperatures. They gradually merge into the structural state of fused minerals similar to that of synthetic glasses quenched from a melt. Shock-fused alkali feldspars can, however, be distinguished from their laboratory-fused counterparts by infrared absorption and by higher density.

Stoeffler, D.↗
NASA NTRS1974

Feldspar basalts in lunar soil and the nature of the lunar continents

It is found that 25% on the Apollo-14 glasses have the same composition as the glasses in two samples taken from the Luna-16 column. The compositions are equivalent to feldspar basalt and anorthosite gabbro, and are similar to the feldspar basalts identified from Surveyor-7 analysis for lunar continents.

Reid, A. M.↗
NASA NTRS2003

Visible/Near-Infrared Spectra of Experimentally Shocked Plagioclase Feldspars

Minerals subjected to high shock pressures exhibit structural changes with increasing pressure (e.g., fractures, deformations, formation of diaplectic glass, and complete melting [1-6]). Petrologic and thermal infrared spectroscopic studies have shown that diaplectic glass (maskelynite) formation in feldspars occurs between ~25-45 GPa, while significant melting occurs above ~45 GPa [7- 12]. Past studies of visible/near-infrared spectra of shocked plagioclase feldspars demonstrated few variations in spectral features with pressure except for a decrease in the absorption feature near 1250 nm and an overall decrease in albedo [13-17]. We report new visible/near-infrared spectra of albite- and anorthiterich rocks experimentally shocked from 17-56 GPa.

Johnson, J. R.↗
NASA NTRS2003

Evidence for Coordination and Redox Changes of Iron in Shocked Feldspar from Synchrotron MicroXANES

Shock modification of feldspar has been documented and experimentally reproduced in many studies since the recognition of maskelynite in Shergotty. Experimentally shocked feldspar samples have been well studied using chemical and crystallographic techniques. The crystallographic, site-specific characterization of major and minor elements is less well documented. We present early x-ray absorption (XAS) spectral data for a suite of albitite samples that were experimentally shocked at pressures between 17 and 50 Gpa.

Delaney, J. S.↗
NASA NTRS1971

Partitioning of Eu and Sr between coexisting plagioclase and K-feldspar.

Minerals were separated by an EM approach and with the aid of liquids of great density. An analysis of K, Rb, Ca, Sr, Ha, and rare earth elements was conducted by means of a mass spectrometer isotope dilution technique. The behavior of the divalent europium ions during the partition process was found to be very similar to that of divalent strontium ions, taking into consideration data of the partition coefficients between coexisting feldspars in acidic rocks.

Nagasawa, H.↗
NASA NTRS1973

Europium anomaly in plagioclase feldspar - Experimental results and semiquantitative model.

The partition of europium between plagioclase feldspar and magmatic liquid is considered in terms of the distribution coefficients for divalent and trivalent europium. A model equation is derived giving the europium anomaly in plagioclase as a function of temperature and oxygen fugacity. The model explains europium anomalies in plagioclase synthesized under controlled laboratory conditions as well as the variations of the anomaly observed in natural terrestrial and extraterrestrial igneous rocks.

Weill, D. F.↗
NASA NTRS1977

Laboratory measurements of upwelled radiance and reflectance spectra of Calvert, Ball, Jordan, and Feldspar soil sediments

An effort to investigate the potential of remote sensing for monitoring nonpoint source pollution was conducted. Spectral reflectance characteristics for four types of soil sediments were measured for mixture concentrations between 4 and 173 ppm. For measurements at a spectral resolution of 32 mm, the spectral reflectances of Calvert, Ball, Jordan, and Feldspar soil sediments were distinctly different over the wavelength range from 400 to 980 nm at each concentration tested. At high concentrations, spectral differences between the various sediments could be detected by measurements with a spectral resolution of 160 nm. At a low concentration, only small differences were observed between the various sediments when measurements were made with 160 nm spectral resolution. Radiance levels generally varied in a nonlinear manner with sediment concentration; linearity occurred in special cases, depending on sediment type, concentration range, and wavelength.

Whitlock, C. H.↗